Acute Chest Syndrome (ACS) is the second most common cause of hospitalizations and the leading cause of death in patients with sickle cell disease. We have found that using secretory phospholipase As levels we can predict which patients with vaso-occlusive crisis will go on to develop ACS. The aims of this study are to: determine if red blood cell transfusion will eliminate or lessen the severity of ACS; and to compare the toxicity of the transfusion intervention with the standard management of ACS.